Telephone



R. P. A. ANDERSSON TELEPHONE Filed Sept. 6. 1921 2 Sheets-Sheet 1 Patented Aug. 5, 1930 PATENT OFFICE RINGHALD PER ALFRED AITDERSSON, OF STOCKHOLM, SWEDEN TELEPHONE Application filed September 6, 192?, Serial No. 217,795 and in Sweden July 13, 1921.

The invention has for object a push button microtelephone, that isto say, a combined microphone and telephone-receiver, similar in shape and size to a push button for electric bells, and intended to be used as a local telephone for different purposes. By the invention it is made possible. to combine the microphone and telephone receiver within the same covering in such a way that the microtelephone thusformed, in shape and size,

most resembles an ordinary push button for electric bells, and in many cases it can be suitably arranged instead of such.

It is characteristic of the invention, that a common membrane is used, which by its one side supports the carbon particles in the microphone and with its other side is near the magnet cores of the electromagnets. This is made possible by the fact that the telephone and microphone are never active atthe same time. 7 It is evident that this common mem' brane must be made of material, which can be influenced by the magnets.

In the accompanying drawing, which shows an example, Fig. 1 is an axial section, Fig. 2' front elevation, Fig. 3 side view and Fig. 1 a diagram of connections for Figs. 1-3.

The device shown in Figs. 1-4 can be used with advantage when a special signalling ar- 9 rangement (electric bell) is arranged and when signals are only given in one direction. WVhen signalling in more than ,one'directlon is desired the device can be provided with asummer or the like.

box d,'inside the upper cylindrical edge of which the cylindrical flange of a metal cover f fits. In order to prevent the covers insertion to more than a certain depth in the box a shoulder is arran ed in the cylindrical inside of the box as well as on the outside of the cover flange. At the bottom of the metal box an ebony holder 6 is fastened by means of a central sleeve, which serves at the same time as an insulator for a screw 1, belonging to the microphone, and passing through the bottom. The ebonite holder 0 has the form of a middle strip and serves as a support for the microphone. One of the raised parts at the ends of the holder 6 serves as a holder The device consists of a cylindrical metal for two slit contact pins2, 3 (only 2 is seen in Fig. 1) whereof 2 by'means of an insulated wire is connected with the screw 1. The microphone consists of a tin box 7, against the bottom of which a carbon cylinder 5 provided with radial rooves is kept pressed by means of a screw 6,which is screwed into a disc on the upper part of the screw 1. In the radial grooves on the carbon cylinder 5 there are two'metal sheets 7 and 8 corresponding in form to the grooves, which metal sheets bytheir elasticity serve in a known way to prevent'the packing of the carbon particles. Said metal sheets are fastened by a piece of felt 9 in the form of a wheel with rim, hub and spokes, in the space between which the carbon particles are lodged. The piece of felt 9 and the carbon particles 10 thus lie tightly against the'membrane 11. The membrane is provided with holes for the contact pins which holes either are, provided with ebonite sleeves or are so large that contact with the pins need not be feared. In order to connect an outer wire to the screw 1 there are two metal discs and an insulated ebonite' disc on the outer side ofthe tin box. In the bottom of the cover there is located an ebonite sleeve 20 for the passage of an insulated Wire 25, which is connected to the contact pin 3,

and there is also on the outside a terminal v screw 21, directly screwed in the metal for; connection to another wire 26.

' The outer side of the metal cover fis perforated for the passing in and out ofthe. sound waves and has a parabolic form for bettering the sound conditions. In the centre of the paraboloid form is mounted a press button 12 formed from suitable insulating material. In the same way that the microphone is fastened to the metal box (Z, the telephone receiver is fastened out-he cover 7. The inner edge of the paraboloid form is providedwith a circular shoulder. Against the shoulder rests the semi-circular shaped bowl magnet 13, and a semi-circular shaped 95 disc of any insulating material In the mid dle of the disc 14; there, are two holes lined with metal sleeves 27, 28, each of which holes is connected with a metal piece for connection to the metal threads. When the device inner end is mounted, the contact pins 2 and 3 pass through respective holes and are each in conductive connection with corresponding metal sleeve that is to say, with 27, 28 respectively. In order to prevent contact between these sleeves and the shoulder surface a piece of mica is placed between this shoulder surface and the disc 14. The steel magnethas branches stretching inwardly radially, at the outer ends of whichthere are holes for theby means of screws and intended to be brought into contact with the screw 18 by means of the push button 12., The magnet spools 2:4 are afterwards arranged around the magnet cores. The contact spring 19, by means of insulated wire, is connected with the metal piece on the metal sleeve 27 and screws 18 are connected in the same way with the metal piece on" the metal sleeve 28. The magnet spools are connected in series and one of the free ends'is joined with the metal cover f and the other with the contact spring 19.

The membranel1 is in conductive connection with the metal box d, thereby. that it is held pressed. against the carbon particles by means of the inner edge of the cylindrical flange'in the metal cover f.

For fastening the cover to the box, there are screws 22, which fit axial. holes extending lengthwise on the covers cylindrical flange. The reason of this arrangement is to be able to regulate the distance of the magnet from the membrane by means of shoving the cover inwards or outwards, andafterwards fastening the cover to the box in the most suitable meansof thescrews 29.. At the of the cylindrical flange on the cover is a plan. circular flange for the fastening ofthe cover, by screws or the like, to its base.

When; a person' A (to the left in Fig. 4 pressesthe button 12, in such a way that the s-pringawptouches the screw 18,. the bell S rings. The: current then goes namely from the battery to thebell S and further through the wire 25, the contact pin 2', the screw 1, and the wire 29' to the battery. 7 I

hen the person 13' (to the right in Fig. 4) is'thus called, ,and lifts, the receiver of his instrument, which can be of the usualtype,

position by a. hook current switch is closed in a known way." By'means of a press current switch, set in thehandle of the receiver or in the microphon-es circuit in a known way, conversation can afterwards he carried on undisturbed with the person A.

When the person A speaks, current flows from the battery through the above mentioned hook switch and passes through As microphone, wire 30, Bs magnet coils to the battery.

When the person B speaks, the current flows from the battery through the above mentioned hook switch and passes through the microphone in Bs telephone, the wire 30, As magnet coils to the battery.

Other embodiments than this are possible. Both devices schematically given in Fig. l could be of the type the inventionintends, whereby the hook switch must be changed for any current switch of another type. Further the plan flange for the fasteningof the device to its base need not be arranged on the cover but may be made as a continuation outwards of the boXs bottom, whereby the whole device is outside the wall. Instead of having the push button in the centre it can be placed at the side of the device, and in the centre can be arranged instead a regulating screw and springs for adjusting the distance of the magnet core from the membrane, whereby the setting by means of the screws 22 is dispensed with. Also the microphone can be made set table in relation to the membrane in like manner by means of regulating screws. Instead of the parabolic buckling on the outside of the cover, there may be a horn with the wider part facing outwards.

For increasing the sound strength, the receiver, can if desired, be provided with a transformer coupled low frequency amplify= ing valve.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is: V 1

A device of the class described comprising a cover, a. telephone receiver and a microphone disposed within the cover, a casing. confining the cover, a single plane diaphragm mounted in the casing, said telephone receiver being disposed upon one side of the diaphragm, said microphone being disposed upon the other side thereof, and a felt member adapted to lie against the carbon particles of the microphone and free against the diaphragm.

In witness whereof, I have hereunto signed my name.

RHNGHALD PER ALFRED ANDERSSQFI. 

